Technical Field
The present invention relates to a crane used to store and pick merchandise trays in/from shelves of an automated warehouse.
Related Art
In conventional automated warehouses, comparatively large amount of articles of the same type are housed in cases and stored in shelves (JP 5382452 B2 and JP 5976388 B2).
In electronic commerce, which significantly grows particularly in recent years, there is a sales technique called the long tail. In the technique, many types of merchandise including ones generating low sales are stocked and customers support the technique. However, for management of inventory of huge types of merchandise in contrast to types of merchandise in conventional store commerce, shelves for storing the merchandise requires vast space, and picking merchandise generates work requiring long time walk between the shelves, which is not efficient. Conventionally, there are known automated warehouses capable of storing merchandise in cases. However, in those automated warehouses, a case is taken out and then a replenishing case is stored, which makes the automated warehouses unsuitable for loose selling of many types and small amount of merchandise from the viewpoint of productivity. Thus, in order to secure space productivity and picking productivity by tray-storing many types of merchandise in high rack shelves having high space productivity, more efficiency such as increasing speed of case processing of a stacker crane is required.
There are many stacker cranes similar to those described in JP 5382452 B2 and JP 5976388 B2. However, such a stacker crane has to move to a conveyor as a base point every time when storing and picking operations have completed, limiting operation efficiency even when travelling speed of the crane and storing/picking speed of transfer devices are increased.